This invention generally relates to burial systems for the disposal of hazardous waste, and is specifically concerned with a vault system for the underground disposal of low-level radioactive waste that is formed from a plurality of vault cells, each of which is inspectable and has its own liquid collection and monitoring system.
Burial systems for the disposal of radioactive waste are known in the prior art. Generally, such burial systems include a floor formed from a generally impermeable material, which may be compacted clay, over which a layer of water-permeable gravel is disposed. The walls and ceilings of such systems may be earthen, or formed from poured concrete. One of the design objectives of such systems is to isolate ground water from radioactive contamination. Ground water can penetrate structural faults in the burial site caused by seismic disturbances or faulty construction, and contamination can be leached out of the radioactive waste deposited in such sites if the waste is submerged in this water for a significant period of time. To prevent ground water from collecting on the floor of such burial sites, a drainage system in the form of a network of drain pipes may be installed between the water impermeable floor and the layer of gravel that forms the bottom of the burial site. In some of these systems, suction is periodically applied to one or more of the drain pipes to see whether or not water has begun to collect therein. In other types of prior art systems, the network of drain files empties into a collection basin which may be periodically monitored.
Unfortunately, there are a number of shortcomings associated with these prior art burial systems that interfere with their ability to reliably and effectively prevent ground water from being contaminated with radioactive waste. For example, many of these systems do not provide an immediate and automatic indication of the presence of a leakage condition. Instead, such a leakage condition can only be found when the system operators take it upon themselves to monitor the water level within the burial site or within a collection basin. Even more importantly, the applicants have observed that none of the prior art systems provides any indication as to the location of a water leakage condition within a particular burial site. This deficiency, in conjunction with the fact that none of these systems provides convenient access to the waste disposed therein once the burial site has been sealed shut, may cause such prior art burial sites to be completely due up and reconstructed when the presence of a leakage condition is detected. The complete reconstruction of such a site and the temporary removal of the waste disposed therein would not only be extremely expensive, but would also expose the workers to potentially harmful radiation.
Clearly, a burial system for the disposition of radioactive waste is needed that automatically provides a clear signal of a leakage condition once water begins to collect therein. Ideally, such a system should have some sort of means for locating the cause of the leakage condition within the burial site, and should further provide some sort of means for readily accessing the waste disposed within the site so that the necessary repairs may be made easily and expeditiously and with a minimum amount of radiation exposure to the workers.